Mailpiece feeders are commonly employed in high-output mailpiece sorters demanding a steady, high-input flow of mailpieces for efficient operation. Therein mailpieces are generally stacked in an up-right position, i.e., on-edge, on a transport deck and shuttled toward a take-out station where the mailpieces are singulated and sorted into one of a myriad of sorting bins/containers. Furthermore, two or more paddles or separator plates may be employed to define compartments therebetween to maintain the on-edge, vertical orientation of the juxtaposed on-edge mailpieces.
Tomiyama et al. U.S. Pat. No. 6,158,732 discloses a sheet feeder for feeding mailpieces in an “upright posture” along a mounting table to a take-out section. More specifically, the mounting table includes a transfer section comprising a plurality of spaced-apart plates or paddles containing a plurality of mailpieces. The paddles, furthermore, are driven linearly along a track which, in turn, moves the mailpieces toward the take-out section of the feeder. The paddles form vertical stanchions/supports i.e., functioning as bookends, to maintain the up-right orientation of the mailpieces as they slide along a linear feed path. While the vertical paddles/plates function admirably to maintain the vertical posture of the mailpieces, the relative spacing therebetween is fixed/constant. Accordingly, unless the combined thickness of the mailpieces equals the dimension between a pair of paddles or, alternatively, is a multiple thereof (when two or more mailpiece compartments are employed), the mailpieces may fill the compartments in a non-optimum manner. That is, either all of the compartments will be slightly under-filled/over-filled, or at least one compartment will only be partially-filled.
Inasmuch as the operation of the take-out section is particularly sensitive to the orientation of, and pressure applied by, the fed mailpieces, any misalignment of the mailpieces or retarding force, can result in a feed failure. For example, a partially-filled compartment may result in a sag/bow in flats mailpieces when standing on-edge. As such, the mailpieces may be fed at an oblique angle, deviating significantly from the desired planar orientation. On the other hand, an over-filled compartment can result in difficulties separating and/or singulating the mailpieces. That is, high friction forces can develop between the mailpieces as the spring stiffness characteristics of the paddles/plates tend to squeeze the mailpieces therebetween. As such, the friction forces retard or otherwise restrict the release of the mailpieces which may adversely impact mailpiece separation/singulation by the take-out belt. It should be appreciated that the take-out belt relies on a known/expected magnitude of friction to remove or separate one mailpiece from another. Consequently, “fixed-pitch” paddles or separation devices often result in the mailpieces being under-filled or over-filled, and exhibit feed failure difficulties such as those described above. Examples of other fixed-pitch separation devices are disclosed in Noguchi et al. U.S. Pat. No. 4,789,148, and Hiromori et al. U.S. Pat. No. 4,523,753.
With regard to the paddle/plate shown in the Tomiyama '732 patent, it will also be recognized that the paddle/plate is adapted to support small, letter-size envelopes or post-card sized sheets. In view of the sensitivity of mailpiece feeders to deviations in mailpiece shape and size, the teachings of the '732 patent are not immediately/directly applicable to full-sized flats-type mailpieces or letter-sized sheet material. That is, the paddle configuration will almost assuredly result in a malfunction when handling/supporting mailpieces which are oversized relative to the paddle, i.e., the unsupported section of the mailpiece potentially resulting in a non-planar orientation.
A variable pitch separation device is disclosed in Antonelli et al. U.S. Patent Application Publication No. US 2004/0113355 A1 wherein a single wedge-shaped blade supports a vertical mail stack of an on-edge mail stacker. The wedge-shaped blade is slideably mounted to and guided by a linear support or bar. Furthermore, the blade is pivotable about the longitudinal axis of the bar so that an operator can rotate the blade upwardly to remove it from the vertical mail stack at a first location and downwardly again to support the mail stack at a second location. While the wedge-shaped blade may be variably positioned relative to the mail stack, the blade is a passive device which slides along the transport deck as additional mailpieces are added to the stack. Furthermore, the blade is generally configured to support letter size envelopes along the long edge of the mailpiece. Moreover, the support system disclosed therein provides a single compartment, i.e., between the single blade and the input belt. Consequently, the single passive blade provides nominal control over the frictional forces developed between the mailpieces and is not configured to support larger, flats mailpieces.
A need, therefore, exists for a mailpiece feeder which minimizes handling malfunctions, optimizes throughput efficiency, and facilitates the stacking/feeding of large quantities of letter-size and flats mailpieces.